Tropical Depression TWO

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TROPICAL DEPRESSION TWO DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022009
1100 AM AST WED AUG 12 2009
 
TROPICAL DEPRESSION TWO SHOWS A CLASSICAL SHEAR PATTERN IN SATELLITE
IMAGERY THIS MORNING...WITH UPPER-LEVEL EASTERLY WINDS DISPLACING
THE CONVECTION TO THE WEST OF THE EXPOSED LOW-LEVEL CENTER.
SATELLITE INTENSITY ESTIMATES HAVE INCREASED TO 35 KT FROM TAFB AND
SAB. HOWEVER...A QUIKSCAT OVERPASS AT 0812Z DID NOT SHOW
TROPICAL-STORM-FORCE WIND VECTORS THAT LOOKED RELIABLE. THUS...THE
INITIAL INTENSITY REMAINS 30 KT FOR THIS ADVISORY. AT THIS TIME...
MOST OF THE LOW-LEVEL INFLOW INTO THE DEPRESSION SEEMS TO BE COMING
FROM THE NORTH...REPRESENTING POSSIBLY MORE STABLE AIR PASSING OVER
COOLER WATERS. THE FLOW ON THE SOUTH SIDE OF THE DEPRESSION IS
FEEDING INTO A LARGE DISTURBANCE BETWEEN THE CAPE VERDE ISLANDS AND
AFRICA.

THE INITIAL MOTION IS NOW 265/11.  THE DEPRESSION IS ON THE SOUTH
SIDE OF A LARGE LOW/MID-LEVEL RIDGE...AND THE LARGE-SCALE MODELS
FORECAST THIS TO CONTINUE FOR THE NEXT TWO DAYS OR SO.  AFTER THAT
TIME...THE MODELS FORECAST A SERIES OF MID/UPPER-LEVEL WEAKNESSES IN
THE RIDGE THAT WOULD STEER THE CYCLONE WEST-NORTHWESTWARD.  THE
TRACK MODEL GUIDANCE MOSTLY AGREES WITH THIS SCENARIO...ALTHOUGH
THERE ARE TWO CLUSTERS IN THE GUIDANCE.  THE HWRF...BAMD...LBAR...
AND CLIPER CALL FOR AN EARLIER WEST-NORTHWESTWARD MOTION...AND AS A
RESULT THEY WIND UP NORTH OF THE OTHER GUIDANCE BY DAY 5.  THE NEW
FORECAST TRACK...WHICH IS ADJUSTED TO THE SOUTH OF THE PREVIOUS
FORECAST...IS DOWN THE MIDDLE OF THE SOUTHERN GUIDANCE CLUSTER IN
BEST OVERALL AGREEMENT WITH THE CONSENSUS MODELS TVCN AND TVCC. 
ALTHOUGH IT APPEARS UNLIKELY...THE UKMET SUGGESTS AN ALTERNATIVE
SCENARIO...WITH THE DEPRESSION WEAKENING AND THE REMNANTS MOVING
WEST INTO THE CARIBBEAN.

THE DEPRESSION IS CURRENTLY OVER SEA SURFACE TEMPERATURES NEAR
27C...AND THE SSTS ALONG THE FORECAST TRACK INCREASE TO 28C AFTER
72 HR.  THE LARGE-SCALE MODELS FORECAST THE DEPRESSION TO ENCOUNTER
MODERATE VERTICAL WIND SHEAR DURING THE FORECAST PERIOD...FIRST
FROM THE EAST AND LATER FROM THE SOUTH AND WEST.  ALSO...WATER
VAPOR IMAGERY SHOWS VERY DRY AIR AT THE MID/UPPER-LEVELS TO THE
NORTHWEST OF THE DEPRESSION.  THE LATTER TWO FACTORS SUGGEST THE
SYSTEM MAY BE SLOW TO STRENGTHEN...AND AT THIS TIME NONE OF THE
INTENSITY GUIDANCE FORECASTS AN INTENSITY OF HIGHER THAN 55 KT
DURING THE FORECAST PERIOD.  THE NEW INTENSITY FORECAST IS SIMILAR
TO THE PREVIOUS FORECAST IN CALLING FOR A 50 KT INTENSITY IN 72
HR...AND IT IS IN BEST AGREEMENT WITH THE SHIPS MODEL.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      12/1500Z 14.3N  33.8W    30 KT
 12HR VT     13/0000Z 14.2N  35.4W    35 KT
 24HR VT     13/1200Z 14.2N  37.6W    35 KT
 36HR VT     14/0000Z 14.2N  40.1W    40 KT
 48HR VT     14/1200Z 14.5N  42.8W    45 KT
 72HR VT     15/1200Z 16.0N  48.5W    50 KT
 96HR VT     16/1200Z 19.0N  54.5W    50 KT
120HR VT     17/1200Z 23.0N  60.5W    45 KT
 
$$
FORECASTER BEVEN
 
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